


Summer Love

by Brewer235



Category: Gravity Falls, Star vs. The Forces Of Evil
Genre: Crossover, Multi, Sibling Incest, Twincest, Twins, straight - Freeform
Language: English
Status: In-Progress
Published: 2020-09-11
Updated: 2020-09-10
Packaged: 2021-03-07 01:55:06
Rating: Explicit
Warnings: Underage
Chapters: 1
Words: 3,367
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26399020
Author URL: https://archiveofourown.org/users/Brewer235/pseuds/Brewer235
Summary: (Co-Author BBandit and ReaperJ) Dipper and Mabel are enjoying their summer when they meet another famous pair of twins on vacation in Gravity Falls.
Relationships: Dipper Pines & Mabel Pines, Marco Diaz (Star vs. The Forces of Evil)/Mabel Pines
Kudos: 4





	Summer Love

"Oh, kids! We're here!" Mr. Diaz shouted into the massive RV camper.

"Honey, we've been on the road for over 10 hours. The kids passed out hours ago." Angie said as she unfastened her seat belt.

"Well, let's get those sleepy heads up and show them the view!" Even after the long trip, Raphael was ready to get the fishing poles out and catch some dinner.

"I'll get the kids." The loving couple shared a kiss before his wife went to the back of the RV. Raphael didn't spare any expenses for the trip. The family had rented one of those bus size campers for the summer.

It was a beauty as the sides popped out and a large master bedroom in the back. Marco and Mariposa decided to get some rest, seeing how things had gotten boring during the trip. Angie opened the door to the room and found her kids cuddling on the bed, Marco was always the big spoon as he held his twin sister tight, "Marcooooo~ Mariposaaaaa~ time to wake up!"

The teens stirred a little as Marco buried his face into Mariposa's bushy brown hair, "Ugh… five more minutes mom." Marco wrapped his arms around his sis a little tighter.

"Mmmmmm… are we there yet?" Mariposa said she snuggled closer to her brother

Angie giggled over how cute they looked, the twins were always close, even to this day. In fact, they slept on the same bed back at home too, "Fine, but hurry up! Your father wants to show you our campsite! We're the only ones here!" Their mother said in an upbeat tone as she left the room and stepped out of the camper.

Marco was rubbing his feet along his sis, "Do I have to get up?" He would rather stay in bed with the little Latina in his arms.

Mariposa felt his hand creep up to one of her breasts while his boner drugged deeper into her soft round rump, "I know right! Let's call it a day and go back to sleep!" She said as her ass rocked along his shaft.

"Mmmmmmm… you think-" Marco started to say until Mariposa sat up on the bed and stretched her arms over her head.

"Nope, we don't have time for that. You know how dad gets when we go to a new place, where the heck is my bra?" She hops off the bed and starts to look around the room covering her chest.

Marco rolls onto his back, "Yeah I know, what in the hell am I to do with this?" He points at the hard area around his crotch.

Mariposa finds her bra and pulls off her shirt, this wasn't making the situation any better for her bro. She looks back in the camp, making sure that the adults are gone. The Latina crawls onto the bed as her large C cup breasts hang off her body, "Wellllll, why don't we go and explore…"

She puts on her seductive eyes as she placed one hand on Marco's hard member on the other on his chest, "Maybe we can find somewhere and have some more fun?"

Marco grins as he pulls his sis onto his lap and takes a long kiss. Mariposa loved it when her brother would get like this. The twins were a lot closer than many of their friends had known of. They shared a little moan as the young man rolled Mariposa onto her back. Marco would always do this to get his way, the kiss deepened as his hand went over to her right nipple and squeezed it.

"Muummp!" Mariposa was losing control, she wanted this just as bad. It was one thing to have fun while their parents were focused on the road.

It was another thing knowing they can walk back into the camper any second! She bits his lower lip before things could get out of hand, "Ouch! What was that for?" Marco pulled away from her and cupped a hand over his mouth.

The Latina rolled off the bed and puts on her bra, "I had to do something! You always get out of control when we start kissing." She pulled on her shirt and flip flops as she walked out of the room.

Marco watched Mariposa walk down the hall and wiggled her ass for him to follow. Her rear always looked sexy when wearing tight booty shirts, "Ohhhhh, I'm so going to get you back for that!" The young man was off the bed and threw on his trademark red hoodie, and boots.

His hoodie was on the tight side nowadays. Marco was a well-known athlete back home with all the numerous positions he held with the various teams at school. Mariposa was the same, the twins were a bit of a celebrity of Echo Creek with the championship they had won over the years.

As he ran out of the camper, Marco was welcomed to the view of a large lake in front of him. The water sparkled as the sun danced on top of it, " Wow…" It was a breathtaking sight with the numerous large trees surrounding the area.

"Yeah… that's what I said!" Mariposa looked up to her bro, he just hit a growth spurt after their 17th birthday. Marco was 6 feet tall now, she was just 3 inches shorter than him now.

"I told you guys the trip was worth it!" Mr. Diaz said as he now wore his fisherman hat and was assembling some rods.

"You were right honey, we just might stay here all summer!" Angie said as she pulled out the grill to cook some dinner when it was ready.

It was a little before sunset as the warm air blew across the family, "Holy crap! Look at that waterfall!" Mariposa pointed out with stars in her eyes.

Marco spotted out a water tower in the distance, "Gravity Falls? Yeah, I can kinda see it now."

Mariposa looked at him with a dumb look, "Of course you would say something like that… I'll race ya!" She shoved him to the side and made a break for the waterfall.

"Why you little!" Marco ran after her.

"Kids!? And they're gone…" Mr. Daiz had hoped they would have helped him with the fishing.

Angie walked to him and wrapped her arm around his waist, "Should have seen that coming, I'll give you a hand, sweety."

"Thank you, dear. Let's see if the fish are biting!" The adults walked over to the lake.

…

Mariposa was covering a lot of distance as she ran faster. She was the fastest runner on the track and field team, "Hurry up you big slowpoke!" She loved to make fun of her bro.

"Mari! You're going to get us lost if you don't slow down!" Marco was having a hard time dodging all the branches.

They passed by the town as the siblings kept on running, "You're just saying that because you're losing!"

The Latina was at the edge of the lake, she could feel the water sprinkling onto her face from the waterfall, "DON'T YOU DO IT, MARI!?" Marco shouted out loud.

She looked over her shoulder and stuck out her tongue, "LATER LOSER!? CANNONBALL!?" A large splashed formed after she entered the lake.

Marco watched, "And she did it…" He assumed a diver's position and followed behind her into the lake.

Mariposa lets the water surround her for a few seconds as she smiled and swam to the waterline, "WOW!? WHAT A RUSH!?" She was threading the water as she waited for her bro to pop up.

Nothing but bubbles were rising from where he landed, "Marco?" She started to look around the area some more.

"Bro? This isn't funny!" The Latina knew Marco was a good swimmer, he was an all-star on the swim team back home.

A minute passed and she started to panic, "MARCO!"

Just as she was about to go back where he had landed, she felt him pop up behind her, "GOT YA!" Marco had wrapped one arm around her neck as the other went over to her stomach from behind.

Mariposa felt like she could jump out of her skin, "AHHHHHH!?" Marco would always do things like this to her.

"YOU IDIOT!?" She pulled his arm to her mouth and bits down on it.

"OUCCCCCH!?" He pulled his arm back and watched her turn to him.

"Serves you right! You know I hate when you do stuff like that!" Mariposa flicked at his nose and swam to the waterfall.

"It's only your fault! Making jump in behind you and not taking off my clothes!" He watched her flip him the bird and kept on swimming.

"Pain in my ass…" Marco followed her.

They came to a stop, a few feet from the waterfall, "Is it me? Or do you see something behind it?" She asked with her head tilted to the side.

"Yeah? Wanna check it out?" He asked and nodded his head over to the waterfall with a little grin.

"Hell yeah, I wanna go!" They dove into the water and swam under the waterfall, just a few feet behind it. Marco was the first one to place his hand onto the ledge and pulled himself up.

"Awww man… I hate wet socks…" He offered a hand to his sis and helped her out.

"Quit crying like a baby!" Marco gave her a dirty look and soon pushed his sister back into the water.

She was taken by surprise as her back smacked onto the water, "Ugh, you dick!"

"You know you love this dick." He said, grabbing his crotch and leaned over with a big grin.

Mariposa watched as the string to his hoodie clung off his body, "Like that's news to anyone!" She then reached up and pulled the strings of his hoodie, Marco followed and was sent headfirst into the water.

He spits out a mouth full of water, "That was a dirty move…"

The Latina was already out of the water as Marco soon chased after his twin, " Come over here you!"

"Catch me if you can- haaaa!" Marco was already on top of her as he pinned her back to the wall.

"You were saying?" He said and came in for a kiss.

Mariposa wasn't upset for long as his tongue entered her mouth, "Mmmmmmm…" She placed her hands on his hip as his body was pressed to her's.

After a bit of making out, they took in the amazing sight of this natural cave, "Woooooow! This place is huge!" Marco releases her and takes in the view while Mariposa wrings and whips her wet hair behind her back and begins to walk around.

"Yeah, this is kinda cool!" Marco followed close behind her as they went deeper into the large open space.

"Do you think anyone else knows about this place?" Mariposa asked the more they explored.

"I would think so… just think of all the things that can be done here, the things we could get away with in here." He grabbed her hand and pulled her into his embrace, holding her stomach and kissing down his neck.

"Oh~ I think I know what we can do! This seems like a good spot." The female twin then turned around and the two came in for a kiss again. Mariposa didn't hold back as she ran a hand under his shirt and the other to his cock.

"Getting frisky are we?" Marco asked as Mariposa was kissing his neck now.

"Maybe, it's not my fault you're so irresistible!" She got down on her knees and started to undo his belt, but something had gotten their attention before they could move on.

"Haa! Dipper!" The twins put a stop to their activities and got down on the ground.

Marco placed a finger over his lips and then threw a thumb to where the sounds were coming from. Mariposa nods and takes points as they crawl towards the commotion that interrupted their fun. They could hear the familiar sound of flesh smacking against each other over and over again.

"Oh, fuck… so tight!" Mariposa comes up to a large rock and looks to the side, Marco was behind her as he did the same.

They could make out an outline of a couple doing the nasty with a small lantern nearby. The Latina grins over the display, "Nice…"

Whoever was fucking right now, it was clear that this wasn't their first go. The male was positioned behind the female as he held her arms behind her and lifted her upper body into the air, "Nice…" Marco also said.

"Ha-harder, Dipper!" The female yelled as her large breast spun in circles over the assault.

Mariposa looked down at her chest, "She's a little bigger than me…" She said in disappointment with a noticeable pout.

Marco placed both his hands onto her breasts, "Maybe, but she doesn't have one of these." He whispered into his sis' ear and twisted the bar in her left nipple.

"Hssss. Good point!" She pulled his right hand under her beltline to play with her pussy. Mariposa couldn't wait to have him inside again, the twins were known to fuck at least 3 times a day.

Her brother smiled as he started to kiss her ear and sunken his fingers deeper into her honeypot, "You know, this is pretty hot. We've never done it with someone else in the same room with us."

"Mmmmmhmmmmm." Mariposa unfastens the button to her booty shorts as she lowered them down to her knees.

Marco was already ahead of her as he unzipped his pants, the couple in front of them kept on going at it some more, "Bend over a little…" He said as Marco grabbed the base of his cock.

Mariposa bit her bottom lips as she lowered herself and lined her wet wanting pussy to him, "Hurry up and stick it in already!"

Not to disappoint, Marco slammed all 9 inches of his man meat into the pussy begging for him to enter. Mariposa really enjoyed that growth spurt. She was about to scream, but her bro placed a hand over her mouth, "Shhhhh…"

"Mmmmmmmmm!" The Latina moaned into his hand as she arched her back and tilted her head to look at him.

Her big brown eyes gazed deep into his, they always looked so much sexier when his cock was in her. The twins come in for a kiss as Marco started to a small rhythm, they had to keep it down and not disturb the other couple, "Fuuuuuuck me, Dipper!"

Marco still had a clear view of the couple as he started to pump deeper into his sis. The Latino moved his left hand under her shirt, he flipped the bra over as Mariposa's breasts. They were free and out into the cool air while they bounced around, "Haaaa… Marco!" She said in a hushed tone.

He grinned as his right hand squeezed her firm booty now, "Tell me how much you like it." Marco was taking his time as he buried himself deeper into Mariposa.

"Oh~ you want me hmmm. Me to tell you how much I love your cock, big bro?" This was something Mariposa loved to do. She was sure to stroke his ego just the way he liked it.

"That's right mmmhmmm. Tell me what I want to hear, Mari." Marco started to pull on the silver bar in her nipple.

She gave him an evil grin as Mariposa pressed her rear harder into him, "My body is yours and all yours, destroy your fucktoy with your thick cock, I only want to be used by you anyone else would just make feel empty, wreck my pussy, destroy my fucking throat just don't stop using me!" She moaned.

"And~?" He asked, wanting more dirty details.

"And I'm your sluttly little bitch!" She was getting warmer.

"And what does my sweet little slut want?" Marco said into her ear and bits the tip.

"I want you to fill up my pussy with your thick hot cock milk and don't you think of pulling out I want you to fill my womb with our inbred children!" She said with pink hearts in her eyes.

God damn did she know how to get his engine going! Marco wrapped his right hand around her throat as he started to fuck her faster. Mariposa felt her body jerking around as her bro's cock went deeper into her cervix, "Ha! Oh-oh-oh fuc-"

The words went silent in her throat as Marco squeezed tighter, "I said, to keep it down!" He started to speed up his pumps as sweat formed on his face. Marco and Mariposa looked over at the couple.

They had switched positions at some point, the male was on top as he held the female's legs in the air, "Ahhhhh! Dipper! Don't stop haaaaa!"

Mariposa knew that exact feeling as her orgasm built up, "Mar~ Marcoooo~ ahhh-" She tried to sing out his name, it didn't work.

Marco knew his sister liked it rough as the grip around her neck tightened, "I know you're close, I can feel it." Her pussy was quivering around his cock, he could feel her juices making a small puddle under them.

He looked down at her fine tight ass as it bounced off his cock, the Latino sent a wad of spit to her other hole, "Mmmmm~" Mariposa knew what was going to happen as her tongue hung out her mouth like a puppy in heat.

"You like that girl?" Marco said before jamming a thumb into her little puckered and twitching asshole.

"HAAA!" Damn right she loved that feeling as Marco started to fuck her harder.

"DIPPPPER!?" The twins almost forgot about the other couple, they could see the female wrap her legs around her partner.

"MABEL!? I'M CUMMING!?" They watched while the couple held each other tight as they started to kiss.

"MMMMMMMMMHMMMM!?" Mariposa soon found out that she really liked to watch others do it. Adding that to the long list of kinks she has. Mariposa started to cum while the Latina squirted on the rock in front of them.

Marco felt her pussy clamp down on him while her backdoor twitched wildly around his thumb, "Oh, you naughty girl! You didn't wait for me to cum with you!" He shoved her up along the boulder.

He was relentless as Marco did his best to catch up to her, "Moore~ Fuck meeeeeee moreeee~" Marco then lifted her left leg pulling it out of her shorts to get himself deeper into his sister.

"God damn! Fuck haaa!" The Latino was having a hard time staying quiet as he started cum. He slammed his body onto her's as Mari was pinned between a rock and a hard dick.

"Haaaaa~ Soooooo fulfill!" Mariposa felt her insides being painted with his cum, it felt so hot as her knees jerked together. Marco grabbed a chunk of her hair and started to pull on it to make sure every inch of him was inside.

"Huh? Did you hear that, Mabel?" Marco gritted his teeth together and tried to keep it down. It was just too damn hard with feeling her pussy sucking him dry.

"Feels so good…" He buried his face into her hair and rode out the rest of the orgasm.

"Shhh! You're being too loud!" Mariposa couldn't deny how hot this was, watching as her brother bounced off her voluptuous ass.

"Yeah, I think so?" Mabel said as she shoved Dipper away to get dressed.

"Marco! Pull out damn it! We need to get out of here!" The Latina jammed her rear into her bro and grabbed her shorts hurrying to put them back on.

"Fuck! I wasn't done yet!" Marco held his cock as some cum was slashed onto her back.

"I don't care! Let's go!" Mariposa was already crawling back to the waterfall.

"Hey did you hear something?" Mabel asked

"Stay here, Mabel I'll check on it." Dipper walked over to the large rock Marco and Mariposa was just at.

"Shit." Marco puts his junk away and disappears into the darkness.


End file.
